Method of making tungsten-carbide alloys



Patented Feb. 17, 1931 UNITED STATES PATENT OFFICE .ro'snrn r. 'rnnax,or Los anonnns, camromna METHOD MAKING TUNGSTE'N-CARBIDE ALLOYS IoDrawing.

tungstenvmetal, usually in a finely comminuted state in a carboncrucible which is heated either by assin an electric current through thecrucible or by means of an electric arc. The high temperatures thusproduced, will fuse the tungsten and in its fused state will absorbcarbon from the walls of the crucible, or inthe case of the electricare,

from the carbon vapor of said are. It is diflicult to control the amountof carbon dissolved in or combined with the tungsten. The tungstencarbide should not have any free carbon which will be present in theform of raphite crystals, but all the carbon should e combined andshould not ordinarily exceed 4%.

The ob'ect of the present invention is to prevent t e formation ofgraphite tungsten crystals or free carbon in the tungsten carbide, thuspreventing the formation of a tungsten alloy which is brittle andfriable, and unsuitable for the cutting medium above mentioned, andalways to insure a tungsten carbide which is of the required degree of.density and toughness.

For this purpose I introduce an oxidizing agent in the mix, which willcombine with thefree carbon, thus preventing the formation of graphiticcarbon, yet will allow the proper amount of carbon to combine with thetungsten. My invention consists of the steps of the method hereinafterdescribed and claimed.

40 I take tungsten, preferably in powdered form and place the samein acarbon crucible 7 cu shape in form, which ma be 2 wide and 1' eep, usinabout 1 of the tungsten metal. I a d thereto tungsten oxide which may beup to of the tungsten metal and subject the same to an electric. arereaching a temperature of about 5000 F. for about two minutes. Thecarbon vapor of the electric arc will combine with-the tungsten 5 toform carbide, but the excess of carbon will Application filed December22, 1928. Serial No. 328,059.

be oxidized, combining with the oxygen of the tungsten oxide, formingcarbon monoxide which will'escape. The molten mass is now poured intomolds, and will contain a tungsten carbide having a carbon content notto exceed approximately 4%.

In place of the tungsten oxide, I may use calcium oxide which willcombine with the excess of the carbon and form calciumcarbide and carbonmonoxide. The calcium carbide will rise to the top of the molten metalas slag. The calcium oxide ma be mixed with a metal charge, or it may eincorporated with the crucible container. The calcium oxide may be usedin any desired amount, but an amount not to exceed 50% by weight of themetal charge is usually suflicient.

It is not essential that pure tungsten oxide be employed. Partiallyoxidized or roasted metail in pulverulent or solid form, may be use Itwill be understood that if desired, other highl refractory metals may beused to form an al 0y with the tun sten. The present in-' vention hasfor its ob]ect, merely the prevention of graphitic carbon.

In place of using singly, either the tungsten oxide or the calcium oxideas an oxidizing agent, I may use a mixture of the two in amountsufficient to prevent the formation of gra hitic carbon.

arious changes in the steps of the method may be made b those skilled inthe art, without departing rom the spirit of my invention as claimed.

I claim:

A method of controlling the carbon content of a tungsten carbide alloy.to prevent the formation of graphitic carbon, OOIIIPIlS? ing addingcalcium oxide to tungsten and fusing the mixture in a carbon crucible.

In testimony whereof I have signed my name to this specificationh JOSEPHT. TERRY."

